1. Field of the Invention
The present invention relates to an image reading apparatus.
2. Description of the Related Art
As one type of original document reading apparatus such as a copying machine, an original document reading apparatus which can select two original document reading modes has been known. The first original document reading mode is stationary original document reading by a flatbed scanner (FBS) which reads an original document, placed on a platen, while moving a reading sensor disposed below the original document. The second original document reading mode is conveyed original document reading in which an original document is read upon being automatically fed by an automatic document feeder (ADF) while a reading sensor is kept stopped at a predetermined position.
An original document reading apparatus of this type includes a main body unit, and an opening/closing unit rotatably supported by the main body unit. The main body unit includes a platen and reading sensor. The opening/closing unit includes a pressure plate and ADF, and opens/closes the platen. US-2008-0266614 discloses an apparatus equipped with a transfer unit which transfers the driving force of a driving source, provided in a main body unit, to the ADF in order to reduce the number of driving sources unique to the ADF so as to keep the apparatus cost low.
In the apparatus described US-2008-0266614, a reading unit which is rectilinearly movable by means of a rack and pinion gear meshes with a second pinion gear disposed at the end of the rack to drive an original document conveyance system. However, a motor is driven in only one direction in original document conveyance, and cannot be driven in a direction opposite to the former. That is, when an original document conveyance driving system is driven in a direction opposite to that in original document conveyance, driving transfer to the original document conveyance system is interrupted, thus changing the original document reading mode to the FB (flatbed) mode. When motor driving of an original document conveyance device is done in only one direction, the initialization operation of the conveyance device, the restoration operation after original document jam processing, and reverse rotation sheet feed which allows original document skew correction (registration) are impossible. Other constraints that, for example, reverse rotation for turning an original document in double-sided reading are imposed. It is therefore inevitable to lower the performance of products by, for example, omission of some functions.